The use of solidification technology and solid block detergents in institutional and industrial operations was pioneered in the SOLID POWER® brand technology claimed for example in Fernholz et al., U.S. Reissue Pat. Nos. 32,762 and 32,818. Additionally, sodium carbonate hydrate cast solid products using substantially hydrated sodium carbonate materials was disclosed in Heile et al., U.S. Pat. Nos. 4,595,520 and 4,680,134, which are herein incorporated by reference in its entirety.
In more recent years, attention has been directed to producing highly effective detergent materials from less caustic materials such as soda ash, also known as sodium carbonate. Early work in developing the sodium carbonate based detergents found that sodium carbonate hydrate-based materials often swelled, (i.e., were dimensionally unstable) after solidification. Such swelling can interfere with packaging, dispensing, and use. The dimensional instability of the solid materials relates to the unstable nature of various hydrate forms prepared in manufacturing the sodium carbonate solid materials. Early products made with hydrated sodium carbonate typically comprised of anhydrous, a one mole hydrate, a seven mole hydrate, a ten mole hydrate or more mixtures thereof. However, after the product had been manufactured and stored at ambient temperatures, the hydration state of the initial product was found to shift between hydrate forms, e.g., one, seven, and ten mole hydrates, resulting in dimensional instability of the block chemicals. In these conventional solid form compositions, changes in water content and temperature lead to structural and dimensional change, which may lead to a failure of the solid form, resulting in problems such as the inability of the solid form to fit into dispensers for use.
Additionally, conventional solid alkaline detergents, particularly those intended for institutional and commercial use, generally require phosphates in their compositions. The phosphates typically serve multiple purposes in the compositions, for example, to control the rate of solidification, to remove and suspend soils, and as an effective hardness sequestrant. It was found, disclosed, and claimed in U.S. Pat. Nos. 6,258,765, 6,156,715, 6,150,324, and 6,177,392, that a solid block functional material could be made using a binding agent that includes a carbonate salt, an organic acetate, such as an aminocarboxylate, or phosphonate component and water. Due to ecological concerns, further work has recently been directed to replacing phosphorous-containing compounds in detergents. In addition, nitrilotriacetic acid (NTA)-containing aminocarboxylate components used in place of phosphorous-containing compounds in some instances as a binding agents and hardness sequestrants, are believed to be carcinogenic. As such, their use has also been curtailed.
The need for solidification matrices for solid, alkaline detergents has required numerous modifications, including removal of phosphorus and/or NTA. Additional modifications include the formulation of solidification matrices incorporating caustic material (sodium hydroxide) in combination with the less caustic materials, such as soda ash (e.g. sodium carbonate), continue to present difficulty in establishing solid, physically stable tablet compositions. It has been shown that highly caustic powders for solidification fail to consistently form stable compositions, such as tablets. Therefore, there is a need for using lower levels of sodium hydroxide in combination with other less caustic materials in order to formulate dimensionally-stable solid compositions. These and other aspects of forming physically stable detergent compositions provide the background against which the present invention is provided.
In an aspect of the present invention, a physically stable phosphate-free alkaline detergent tablet composition for combination ovens is provided.
In an aspect of the present invention, methods for employing ash- and/or hydroxide-hydration to form a physically stable, phosphate-free alkaline detergent tablet containing sodium carbonate, sodium hydroxide and sodium metasilicate are provided.
In a further aspect of the invention, the compositions and methods of the invention provide physically stable compositions having durable cleaning performance, including for example in cleaning combination ovens.